Influence of Listeria innocua on the growth of Listeria monocytogenes

Carvalheira, Ana; Eusébio, Cátia; Silva, Joana; Gibbs, Paul; Teixeira, Paula

doi:10.1016/j.foodcont.2010.04.021

Cited by 35 publications

(31 citation statements)

References 28 publications

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“…No obvious correlations were observed between growth rate and final enrichment populations of each Listeria species or between the ability to produce inhibitory substances and the populations of each Listeria species during the enrichment period. A similar situation also was reported for artificially contaminated milk (6). The presence of L. innocua in test samples can hinder both the detection and recovery of L. monocytogenes.…”

supporting

confidence: 76%

Postenrichment Population Differentials Using Buffered Listeria Enrichment Broth: Implications of the Presence of Listeria innocua on Listeria monocytogenes in Food Test Samples

Keys

Dailey

Hitchins

et al. 2013

Journal of Food Protection

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The recovery of low levels of Listeria monocytogenes from foods is complicated by the presence of competing microorganisms. Nonpathogenic species of Listeria pose a particular problem because variation in growth rate during the enrichment step can produce more colonies of these nontarget cells on selective and/or differential media, resulting in a preferential recovery of nonpathogens, especially Listeria innocua. To gauge the extent of this statistical barrier to pathogen recovery, 10 isolates each of L. monocytogenes and L. innocua were propagated together from approximately equal initial levels using the current U.S. Food and Drug Administration's enrichment procedure. In the 100 isolate pairs, an average 1.3-log decrease was found in the 48-h enrichment L. monocytogenes population when L. innocua was present. In 98 of the 100 isolate pairs, L. innocua reached higher levels at 48 h than did L. monocytogenes, with a difference of 0.2 to 2.4 log CFU/ml. The significance of these population differences was apparent by an increase in the difficulty of isolating L. monocytogenes by the streak plating method. L. monocytogenes went completely undetected in 18 of 30 enrichment cultures even after colony isolation was attempted on Oxoid chromogenic Listeria agar. This finding suggests that although both Listeria species were present on the plate, the population differential between them restricted L. monocytogenes to areas of the plate with confluent growth and that isolated individual colonies were only L. innocua.Despite the relatively low number of annual incidences of foodborne illness caused by Listeria monocytogenes, this organism remains a human health concern because of its ability to grow in many different foods stored at low temperatures and the severity of the illness that it can cause, particularly in susceptible populations. Although the use of molecular-based detection platforms is increasing in the area of food safety, traditional culture-based methods are still more commonly used for the analysis of official test samples, including those † This work is the sole opinion of the authors and does not reflect the official position of the U.S. Food and Drug Administration. No inference of recommendation or criticism should be made based on the inclusion or omission of specific commercial trade names within this publication. * Author for correspondence. ronald.smiley@fda.hhs.gov. ‡ Retired. HHS Public Access Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript suspected of contamination with L. monocytogenes. To detect and recover low levels of foodborne pathogens, a 1-to 2-day enrichment period is normally used. The ideal selective enrichment medium establishes a growth environment in which the target organism is capable of multiplying while populations of nontarget organisms remain stagnant or decline. Unfortunately, selective enrichment media rarely, if ever, have absolute specificity. Thus, target and uninhibited nontarget organisms compete for growth space, which can ultimat...

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supporting

confidence: 76%

Postenrichment Population Differentials Using Buffered Listeria Enrichment Broth: Implications of the Presence of Listeria innocua on Listeria monocytogenes in Food Test Samples

Keys

Dailey

Hitchins

et al. 2013

Journal of Food Protection

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“…It is possible to have falsenegative results for the presence of L. monocytogenes when L. innocua is present. However, bacterial strains may behave differently, particularly when the concentrations of these two species in the sample differ (12). No further experiments were performed on strains isolated from collected flies to determine the possibility of inhibition among Listeria species and/or strains.…”

Section: Discussionmentioning

confidence: 99%

Prevalence and Relative Risk of Cronobacter spp., Salmonella spp., and Listeria monocytogenes Associated with the Body Surfaces and Guts of Individual Filth Flies

Pava‐Ripoll

Pearson

Miller

et al. 2012

Appl Environ Microbiol

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Although flies are important vectors of food-borne pathogens, there is little information to accurately assess the food-related health risk of the presence of individual flies, especially in urban areas. This study quantifies the prevalence and the relative risk of food-borne pathogens associated with the body surfaces and guts of individual wild flies. One hundred flies were collected from the dumpsters of 10 randomly selected urban restaurants. Flies were identified using taxonomic keys before being individually dissected. Cronobacter spp., Salmonella spp., and Listeria monocytogenes were detected using the PCR-based BAX system Q7. Positive samples were confirmed by culture on specific media and through PCR amplification and sequencing or ribotyping. Among collected flies were the housefly, Musca domestica (47%), the blowflies, Lucilia cuprina (33%) and Lucilia sericata (14%), and others (6%). Cronobacter species were detected in 14% of flies, including C. sakazakii, C. turicensis, and C. universalis, leading to the proposal of flies as a natural reservoir of this food-borne pathogen. Six percent of flies carried Salmonella enterica, including the serovars Poona, Hadar, Schwarzengrund, Senftenberg, and Brackenridge. L. monocytogenes was detected in 3% of flies. Overall, the prevalence of food-borne pathogens was three times greater in the guts than on the body surfaces of the flies. The relative risk of flies carrying any of the three pathogens was associated with the type of pathogen, the body part of the fly, and the ambient temperature. These data enhance the ability to predict the microbiological risk associated with the presence of individual flies in food and food facilities.

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“…Commonly used selective enrichment formulations do not display absolute species level specificity resulting in competition between L. monocytogenes and non-target background microorganisms (Dailey et al, 2014;Dallas et al, 1991;Tran et al, 1990) and between L. monocytogenes and the non-pathogenic species, Listeria innocua (Besse et al, 2005;Carvalheira et al, 2010;Curiale and Lewus, 1994;Keys et al, 2013;Petran and Swanson, 1993). Competition results in limited growth and ultimately a reduced final population of L. monocytogenes which lowers the overall sensitivity of subsequent detection platforms and hinders recovery.…”

Section: Introductionmentioning

confidence: 99%

Effect of Listeria seeligeri or Listeria welshimeri on Listeria monocytogenes detection in and recovery from buffered Listeria enrichment broth

et al. 2015

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The presence of multiple species of Listeria in regulated food products is not uncommon and can complicate the recovery of Listeria monocytogenes particularly on a non-differentiating medium. The potential complications of Listeria seeligeri and Listeria welshimeri on the recovery of L. monocytogenes from inoculated food test samples using the U.S. Food and Drug Administration's (FDA) selective enrichment procedure was investigated. Post-enrichment enumeration, in the absence of food product, indicates that some L. seeligeri and L. monocytogenes pairings may have population differentials as great as 2.7 ± 0.1 logs with L. seeligeri being the predominant species. A similar observation was noted for L. welshimeri and L. monocytogenes pairings which resulted in population differentials as large as 3.7 ± 0.2 logs with L. welshimeri being the predominant species. Select strain pairings were used to inoculate guacamole, crab meat, broccoli, and cheese with subsequent recovery by the FDA Bacteriological Analytical Manual (BAM) method with 10 colonies per sample selected for confirmation. The presence of L. seeligeri had little effect on the recovery of L. monocytogenes. The presence of L. welshimeri resulted in the failure to recover L. monocytogenes in three out of the four food matrices. This work extends the observation that nonpathogenic species of Listeria can complicate the recovery of L. monocytogenes and that competition during selective enrichment is not limited to the presence of just Listeria innocua. Keywords

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Influence of Listeria innocua on the growth of Listeria monocytogenes

Cited by 35 publications

References 28 publications

Postenrichment Population Differentials Using Buffered Listeria Enrichment Broth: Implications of the Presence of Listeria innocua on Listeria monocytogenes in Food Test Samples

Postenrichment Population Differentials Using Buffered Listeria Enrichment Broth: Implications of the Presence of Listeria innocua on Listeria monocytogenes in Food Test Samples

Prevalence and Relative Risk of Cronobacter spp., Salmonella spp., and Listeria monocytogenes Associated with the Body Surfaces and Guts of Individual Filth Flies

Effect of Listeria seeligeri or Listeria welshimeri on Listeria monocytogenes detection in and recovery from buffered Listeria enrichment broth

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